Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/4007—Curing agents not provided for by the groups C08G59/42 - C08G59/66
  • C08G59/4078—Curing agents not provided for by the groups C08G59/42 - C08G59/66 boron containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
  • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
  • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
  • C08G59/50—Amines
  • C08G59/5046—Amines heterocyclic

Definitions

• the present invention relates generally to compositions and processes for curing epoxy resins and products resulting therefrom. More particularly, the invention relates to new processes for curing epoxy resins, unique boron containing inorganic curing agents, and to the very useful products produced thereby.
• the present invention provides a new process for curing and resinifying epoxy resins into crosslinked polyethers, and particularly but not exclusively epoxy resins of the type represented by the glycidyl polyethers of polyhydric phenols and polyhydric alcohols, which comprises mixing and reacting the epoxy resin With a chloroborazine as shall hereinafter be described in detail.
• the invention further provides resinous products which are thermally stable, and possess good flexural strength as shall also appear hereafter.
• the three membered ring of the epoxide group is highly reactive.
• the ring opening is accompanied by formation of addition compounds.
• the ring opening normally occurs upon treatment ofthe epoxy resin with a reagent having the propensity to open the ring and to polymerize the resin chain to form a resinous product. Polymerization may result in linear polymers or cross linked resins depending upon the functionality of the reagent. In the latter case, these reagents are called curing agents or hardening agents.
• Epoxy resins such as those obtained by reacting epichlorohydrin with polyhydric phenols in the presence of caustic, have heretofore been cured with various organic substances including the primary and secondary polyamines, the tertiary amines, organic acids, organic acid anhydrides and, more recently, with borontrifluorideamine complexes. The use of these materials has, however, not been entirely satisfactory for certain applications.
• amine curing agents for example, give resinous products which fail to retain their hardness and strength at elevated temperatures.
• the amine type curing agents such for example as diethylene-triamine and dimethylamine, are extremely fast acting when used with the glycidyl polyethers. As a result, such resins must be used almost immediately after the curing agent is admixed therewith. Unused portions of the mixture have to be thrown away to prevent its hardening or setting up in the mixing container.
• many of the amines are highly toxic, and certain of them are highly odoriferous and generally unpleasant to handle.
• the borontrifluoride-amine complexes have also proved to be not too useful as commercial curing agents for epoxy resins because the mixture of BF -arnine complex and epoxy resin has a relatively short pot life and must be used very quickly after its preparation. This is especially undesirable for the operators of small plants since they need a resinous mixture which can be utilized over a long period of time.
• the cured products obtained by the use of the BE -amine complexes fail to have the flexibility and impact strength required for many industrial applications.
• one of the primary objects of the present invention is to provide a new process for curing epoxy resins which eliminates many of the disadvantages attending prior processes.
• Another object is to provide a method for curing epoxy resins which gives cured resinous products having improved properties.
• a still further object is to provide improved curing agents which, when employed with epoxy resins, provide an easily handled system for the production of dimensionally stable polyethers.
• Still a further object is to provide an improved curing agent for epoxy resins which is inorganic in composition and contains chloroborazine as an essential ingredient.
• POLYEPOXIDE Epoxy resins as that term is used herein, defines those partially polymerized organic compounds having a 1,2-epoxy equivalency of greater than unity.
• Epoxy equivalency means the number of 1,2-epoxy groups, viz.,
• the epoxy equivalent will be the integer two.
• the compound consists of a mixture of molecules having differing molecular weights and differing numbers of epoxy groups. In this case, the epoxy equivalent will, of necessity, be greater than unity and not necessarily an integer.
• a glycidyl ether particularly suitable'in the practice of the present invention as shall hereinafter appear is the reaction product of reacting 2,2-bis(4-hydroxyphenyl) propane, (Bisphenol A) with epichlorohydrin in the presence of an alkali ac cording to the reaction:
• the product III will on the average contain two epoxy groups per molecule (one at each end) and its epoxy equivalent will be 2. If a 1:1 mole ratio of reactants is used, the product will have an average of 1 epoxy equivalent per molecule. in the present invention for, as indicated above, to be an epoxy resin in terms of this invention, the epoxy equivalent must be greater than 1.
• the glycidyl ethers used in this invention may contain the elements: carbon, hydrogen, oxygen and silicon. They include the 1,2-epoxy polyethers of such poly'hydric alcohols as ethylene glycol, propylene glycol, trimethylene glycol, diethylene glycol, triethylene glycol, glycerol, dipropylene glycol, 1,2-tetramethyl disilanol and the like.
• Epoxide 201 manufactured by Union Carbide, New York, New York, which is 3,4-epoxy-6-methyl cyclohexylmethyl-3,4-epoxy- 6-methyl cyclohexanecarboxylate.
• Epoxide 201 type resins are of the so-called quick setting type resins and, while they require prompt handling, the curing agents of the present invention, as shall appear, are quite eifective with these also.
• Epon 828 which is manufactured by the Shell Chemical Company of Chicago, Illinois.
• Epon 828 is an epoxy resin of diglycidyl ether of Bisphenol A and epichlorohydrin and has the general chemical structure indicated by III in the equation set forth above where 11. may be 0, 1, 2, etc.
• CHLOROBORAZINES AND PREPARATION THEREOF Chloroborazines defines those benzenelike compounds having a planar ring containing three atoms of boron (B) and three atoms of nitrogen (N) in juxtaposition with each other, and in which the hydrogen (H) atoms attached to the boron atoms have been replaced by chlorine (Cl) atoms, and the hydrogen atoms connected to the nitrogen atoms remain, a part or all of them being replaced by a substituent selected from the group consisting of the alkyl and aryl radicals, such for example as CH C H C H etc., as alkyls, and C H (phenyl) as aryls.
• the general mechanism of the epoxy resin-curing agent system of the present invention is that the curing agent possesses the propensity to open the epoxy rings of the epoxy resin and polymerize the resin by linking thereto. It has been determined that cross linking is likewise initiated during the initial cure which occurs, preferably, upon heating to about 140 C. The cross linking is completed by post curing, either with or without the application of additional heart. The post cure is accelerated by the heat which seems to inspire molecular movement out of blocking relationships to expedite the completion of the cross linking.
• PROCESSES AND POLYETHER PRODUCTS 4 are presented to exemplify, and not to limit, the processes which may be employed in the practice of the presentinvention.
• Example 1 Six parts by weight B-trichloroborazine are added to parts by weight of Epon 828 and the reagents are warmed to C. where they are held for about ten' minutes to effect the dissolution of the chloroborazine.
• Example II Four p.p.h. of B-trichloroborazine are mixed with Epon 828 at 140 C. The mixture is then stirred to assure its homogeneity and cast into preformed molds. The cast samples are then cured at about 150 C. for two hours and post cured at about 200 C. for two hours. This sample is then tested. Results of such tests are reported below.
• Example III Six p.p.h. of B-trichloroborazine are mixed with Epon 828 at about 165 C. and the mixture stirred slightly to insure its homogeneity. After about ten minutes of heating, the mixture was poured into precast molds. The cast samples were cured at about 180 C. for one hour and post cured at 200 C. for four hours. The samples were tested. Results of such testing are set forth below.
• Example V Eight parts of B-trichloro-N-trimethylborazine are mixed with 100 par-ts Epon 828 at about 165 C. and stirred. After about seven minutes, the mixture was cast into molds. The cast resin was cured at about 200 C. for 18 hours. The electrical properties of the cured epoxide were measured and are reported in Table V.
• the exigencies of a particular application make it desirable that a post cure be completed quickly and before the polymer is placed in service, it can be achieved by heating the preformed initially cured polymer to a temperature of about 180-200 C. whereupon the heat increases the freedom of molecular motion in the polymer, reduces its density and substantially accelerates to completion the cross linkage reactions already begun.
• the ratio of curing agent to resin should fall between about 4 and 8 parts per hundred.
• the resulting polymer contains considerable unreacted resin with the result that its mechanical and electrical properties are poor to unsatisfactory.
• the resulting polymer contains considerable unreacted resin with the result that its mechanical and electrical properties are poor to unsatisfactory.
• more than about 8 phr. of curing agent/ resin it will be increasingly diflicult to get all of the chloroborazines into solution and the resultant polymer containing unsolubilized curing agent will have reduced thermal properties.
• such a polymer will have substantially no water stability.
• the introduction of curing agent per hundred parts of resin may be increased up to the solubility limits of the mixture.
• the polyether products of the present invention possess high thermal stability and rate Well under testing according to the ASTM Standards on Plastics.
• the properties of the polyether formed by mixing a '7 suitable amount of a chloroborazine with Epon 828 to form a homogeneous mixture in the manner indicated above, initially curing the mixture and, if indicated, post curing the initially cured resin.
• a heat curable composition comprising a polyepoxide having a l epoxy equivalency greater than 1.0 and about 4 to about 8 parts per hundred by weight of a B-trichloroborazine having the general structural formula t?
• R Cl epoxide is 3,4-epoxy 6 methylcyclohexylmethyl-3,4'
• composition of claim 1 wherein the polyepoxide is a glycidyl polyether of a polyhydric alcohol having a 1,2-epoxy equivalency greater than 1.0.
• composition of claim 1 wherein the polyepoxide is a glycidyl polyether of a polyhydric phenol having a 1,2-epoxy equivalency greater than 1.0.
• composition of claim 6 wherein the glycidyl polyether of a polyhydric phenol is the condensation product of epichlorohydrin and 2,2-bis (4-hydroxyphenyl) propane.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Epoxy Resins (AREA)

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Applications Claiming Priority (1)

Publications (1)

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Citations (4)

• 1961
  • 1961-06-01 US US114035A patent/US3261783A/en not_active Expired - Lifetime
• 1962
  • 1962-05-22 GB GB19664/62A patent/GB998267A/en not_active Expired
  • 1962-05-30 FR FR899324A patent/FR1324094A/fr not_active Expired

Patent Citations (4)

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